In accordance with the customary prior art for FPBGA housings (FPBGA: Fine Pitch Ball Grid Array), caBGA housings (caBGA: Chip Array Ball Grid Array) or TFBGA housings (TFBGA: Thin Fine Pitch Ball Grid Array Package), the packages are provided with an interposer substrate, for example made of a bismaleimide triazine resin. The BGA housings are characterized by the fact that component terminals are applied on their underside area in the form of solder balls.
The solder balls are applied by means of a so-called ball placement. During this method, the solder balls are introduced into a flux in the envisaged contact locations in the form of a ball grid array situated on the interposer. In its conventional form, this ball placement is very complicated and very demanding in terms of process engineering.
The conventional ball placement for an FPBGA package construction is characterized by the fact that firstly a water-soluble, rosin-containing flux is applied to the interposer substrate. This flux has the task of breaking up the oxide layers on the conductive tracks on the interposer substrate and on the solder balls and of making the surfaces wettable. The solder balls placed into the flux are subsequently held at the introduction location by adhesion forces.
In the subsequent reflow soldering process in a soldering furnace, the solder balls are then fused onto the interposer substrate in a multizone cycle at temperatures of 110° C. to 225° C. In this case, the soldering temperature is dependent on the solder materials used.
In order that the flux residues are removed again after the fusing operation, the interposer is subsequently cleaned, preferably by means of spray washing.
The solder balls mounted on the interposer in this way then have to take up in part considerable shear forces after the mounting of the BGA assembly on a printed circuit board, which arise as a result of the thermally governed different coefficients of expansion of the materials involved.
DE 198 33 131 A1 describes a method for the contact-connection of electronic components on flexible substrates, in which semiconductor chips provided with FBGA contact terminals are pressed in a force-locking or positively-locking manner onto the flexible substrate provided with a corresponding contact structure. Utilizing the elasticity of the flexible substrate for contact production ensures that a reliable contact-connection is affected even when the microballs have small size deviations.
What is disadvantageous in this case is that, on the one hand, the placement of the semiconductor chips has to be effected with high accuracy for lack of floating effects and that, on the other hand, quite large-area contacts with elevated contact resistance arise.
Finally, WO 97/00598 (U.S. Pat. No. 6,321,443) describes a connection substrate comprising a dielectric, in the case of which areal connection structures are provided on both sides. Metallized vias as the connection elements are connected to one another. However, this connection element is not suitable for the contact-connection of BGA housings.